电网磁暴灾害风险影响因素研究综述

磁暴是源自太阳磁场剧烈变化的地球空间效应,随着电网规模的增大和电压等级的增高,磁暴灾害已经成为诱发电网故障风险的威胁之一.研究电力系统磁暴灾害风险的影响因素可为预防与控制其引发的电网事故提供重要参考.在分析历史典型磁暴事件的基础上,剖析了磁暴诱发电力系统故障的机理,阐述了故障传播与电力系统响应的过程,总结了近年来关于影响电力系统的地磁感应电流水平及其产生的变压器无功损耗方面的研究成果,从磁暴本身的特点和电力系统的参数与结构两方面将影响因素分类.以GIC标准模型,通过改变磁暴扰动环境和电力系统参数,说明了各因素对电网磁暴灾害风险的影响程度,并比较了不同因素影响后果的差异,最后指出了尚未解决的问题和可能的研究方向.     

Review On The Calculation Of Surface Electric And Magnetic Fields And Of Geomagnetically Induced Currents In Ground-Based Technological Systems

Space weather is a popular and important research topic today. Its origin isin the Sun. Space weather effects extend to the surface of the Earth where theyare usually called GIC referring to geomagnetically induced currents intechnological systems such as electric power transmission grids, oil and gaspipelines, telecommunication cables and railway equipment. GIC are a possiblesource of problems within such systems, and observations have been made sincethe first telegraph systems in the 1800's. This paper is a summary and reviewof present knowledge and of possibilities of modelling GIC in a system.Modelling efforts require a determination of the electric field occurring inconnection with a magnetic storm at the Earth's surface and a calculation ofthe resulting GIC. Different modelling techniques of the electric and magneticfields are evaluated in this paper, and special attention is paid to thecomplex image method (CIM) which is suitable for time-critical purposes likeforecasting of GIC. A discretely-earthed power system and a buried pipelineneed different calculation methods of GIC. The former can be treated by amatrix formalism while the distributed-source transmission line (DSTL) theoryis applicable to the latter.     

Electric field at the seafloor due to a two-dimensional ionospheric current

The relation between the seafloor electric field and the surface magnetic field is studied. It is assumed that the fields are created by a 2-D ionospheric current distribution resulting in the E-polarization. The layered earth below the sea water is characterized by a surface impedance. The electric field at the seafloor can be expressed either as an inverse Fourier transform integral over the wavenumber or as a spatial convolution integral. In both integrals the surface magnetic field is multiplied by a function that depends on the depth and conductivity of the sea water and on the properties of the basement. The fact that surface magnetic data are usually available on land, not at the sea surface, is also considered. Test computations demonstrate that the numerical inaccuracies involved in the convolution method are negligible. The theoretical equations are applied to calculate the seafloor electric fields due to an ionospheric line current or associated with real magnetic data collected by the IMAGE magnetometer array in northern Europe. Two different sea depths are considered: 100 m (the continental shelf) and 5 km (the deep ocean). It is seen that the dependence of the electric field on the oscillation period is weaker in the 5 km case than for 100 m.     

Fundamentals about the flow of geomagnetically induced currents in a power system applicable to estimating space weather risks and designing remedies

Geomagnetically induced currents (GIC) in technological systems, like electric power transmission grids, at the Earth's surface are caused by space weather processes, whose origin is in the Sun. In power systems, transformers may be saturated due to GIC leading to different problems extending from an increase of harmonics to a blackout of the system and damage of transformers. To design reasonable measures against impending problems, GIC magnitudes in the network should be estimated in different circumstances. This paper tackles basic features of GIC flow in a fictitious five-transformer/four-line power system, which is simple enough to make the equations easily manageable but complex enough to yield real and usable information. It is shown that the direction of the geoelectric field affects GIC at different sites but the dependence is not straightforward since GIC produced in one part of the system flows to others. Generally, transmission lines experience much larger GIC than transformers. Series capacitors in transmission lines prevent the flow of dc-like GIC but, without a careful analysis, their installation may result in larger GIC at some transformers of the system thus increasing the risk of problems.     

中国广东电网的几次强磁暴影响事件

2001年以来,随着我国阳\|淮系统等多条500 kV长距离线路的相继建成投运,江苏上河、广东岭澳等地变压器多次发现不明原因的强烈振动和噪声增大事件.本文通过对2004年11月以来、十几次磁暴地磁数据与变压器中性点实测电流数据的比较,证明了干扰事件是磁暴在电网产生的地磁感应电流（GIC）所为;其中,2004年11月7日和10日磁暴在岭澳核电站引发的GIC最大值为47A和55.8A,大于直流输电单极运行时变压器中性点的直流电流水平,因此磁暴对岭澳核电站的瞬时影响比直流输电的影响大;监测数据表明广东电网的GIC水平高于阳淮输电系统的水平,初步分析认为与电网结构和海岸效应等因素有关.目前,举世瞩目的1000 kV特高压工程已开工建设,特高压线路的单位电阻最多是500 kV的二分之一,并且线路更长、规划规模大、且变压器采用单相变压器组结构,磁暴影响问题迫切需要研究.     

Geomagnetically induced currents in the Finnish high-voltage power system

We consider geomagnetically induced currents (GICs) in power systems from the viewpoint of a geophysicist. Special attention is paid to the Finnish high-voltage power system, in which exact theoretical model calculations together with recordings have been performed for several years. We present several examples of theoretically computed GICs using different geophysical models for estimating the geoelectric field driving GICs. Statistical prediction of GICs is outlined referring to studies made in Finland. We show that a combination of GIC recordings at few sites with theoretical modelling of ionospheric currents and the earth's conductivity, and data of geomagnetic activity makes it possible to derive GIC statistics of the entire power system. Finally, we discuss requirements for a long-range prediction of GICs, which will obviously be a widely-studied topic in future.     

地磁感应电流（GIC）的作用与评估

地磁感应电流（GIC）可能对各种人工长距离导电体造成影响与危害.地磁扰动产生的感应电场的强度与地磁场强度、地下电阻率结构相关，在导电系统内生成的GIC的强度则同时与导电系统的内在结构有关.计算了加拿大Manitoba省三个典型地区在2000年7月15日的一个强烈磁暴期间产生的感应电场.通过对地磁活动性的统计分析，估计加拿大魁北克电网可能经受的最大GIC达每相78A（一年一次）和234A（每十年一次）.     

A Review of Studies on the Telluric Currents

This paper reviewed the history of telluric current research, and the recently achieved results, including telluric current field source, transmission, spectral characteristics, and focused on the discussion of the application of telluric current and its relationship with seismic activities and so on. Meanwhile some new cognition of telluric current study was proposed. What’s more, based on the latest telluric current research and new data processing new method, five new ideas on telluric current research were summarized. The demonstration of new results and new methods of telluric current study may promote further research on it and also it has certain enlightenment significance to explore better data processing methods and the development of the subject.     

华北地区地电暴时GIC及涡旋电流响应分析

通过地电场台址近地表介质电阻率和地电场值计算大地电流,从大地电流场中分离出涡旋电流;根据平面波理论和水平导电层模型,使用地磁暴观测数据在频率域计算地磁感应电场(GIE),由GIE计算地磁暴感应电流(GIC).计算结果与实测值对比分析表明:GIE计算结果与实测地电暴具有很好的相位一致性;GIC涡旋中心相对地电暴涡旋中心存在向SE漂移约3°的现象;磁暴时地磁场Z分量的幅值分布图中极大值区域与涡旋中心重合,可能是GIC涡旋中心偏移的原因.另外,根据电磁感应原理提出的等效环电流模型,在一定程度上解释了涡旋大地电流的形成机制.本项工作可应用于地磁观测与地电观测的相互校正,同时有助于认识地电暴对大地电流分布的影响.